Base Class Access Specifier on the Table 15-1
The base class access specifier determines the access privillege of a derived class to its base class.
In this exercise, we are going to inspect the access at three different scope:
1. Inside the Base class by the base class constuctor.
2. Inside the Derived class by the derived class constructor.
3. At the application , by referencing to the instance methods.
Detail information on the requirement is inside the starter.
Starter: lab11_starter.cpp
Submit: lab11.cpp
Table 15-1
Base Class Access
Specification How Members of the Base Class Appear in the Derived Class.
private
Private members of the base class are inaccessible to the derived class.
Protected members of the base class become private members of the
derived class.
Public members of the base class become private members of the derived class.
protected
Private members of the base class are inaccessible to the derived class.
Protected members of the base class become protected members of the
derived class.
Public members of the base class become protected members of the derived
class.
public
Private members of the base class are inaccessible to the derived class.
Protected members of the base class become protected members of the
derived class.
Public members of the base class become public members of the derived class.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lab11_starter.cpp is
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <iostream>
class Base
{
public:
int mPublic;
private:
int mPrivate;
protected:
int mProtected;
public:
Base() : mPublic(0), mPrivate(0), mProtected(0) {
std::cout << “nmPublic: ” << mPublic << std::endl
<< “mPrivate: ” << mPrivate << std::endl
<< “mProtected: ” << mProtected << “n … created Basen”;
}
int get_mPublic() {return mPublic;}
int get_mPrivate() {return mPrivate;}
int get_mProtected() {return mProtected;}
};
class Pub: public Base
{
public:
// Public inheritance means:
// mPublic stays public
int get_Pub_mPublic() { return mPublic; }
// mPrivate becomes inaccessible
// mProtected stays protected
int get_Pub_mProtected() { return mProtected; }
Pub()
{
// The derived class always uses the immediate parent’s class access specifications
// Thus, Pub uses Base’s access specifiers
mPublic = 1; // okay: anybody can access public members
//mPrivate = 2; // not okay: derived classes can’t access private members in the base class!
mProtected = 3; // okay: derived classes can access protected members
std::cout << ” … inherited and modified by cPubn”
<< “mPublic: ” << mPublic << std::endl
<< “mPrivate not available, use get_mPrivate(): ” << get_mPrivate() << std::endl
<< “mProtected: ” << mProtected << “n … created cPubn”;
}
};
class Pri: private Base
{
// Fill the blank with
// 3 getters, if possible.
// Default constructor with same initialization values (1, 2, 3) , if possible.
// Also, make the Default constructor display the private data values, either accessing directly or via base class getter.
// If the above required feature can not be done, explain why in comment.
};
class Pro: protected Base
{
// Fill the blank with
// 3 getters, if possible.
// Default constructor with same initialization values (1, 2, 3) , if possible.
// Also, make the Default constructor display the private data values, either accessing directly or via base class getter.
// If the above required feature can not be done, explain why in comment.
};
int main()
{
// Outside access uses the access specifiers of the class being accessed.
// In this case, the access specifiers of cPub. Because Pub has inherited publicly from Base,
// no access specifiers have been changed.
std::cout << “n … creating cPub”;
Pub cPub;
cPub.mPublic = 4; // okay: anybody can access public members
// cPub.mPrivate = 5; // not okay: can not access private members from outside class
//cPub.mProtected = 6; // not okay: can not access protected members from outside class
std::cout << ” … access cPub by applicationn”
<< “cPub.get_Pub_mPublic(): ” << cPub.get_Pub_mPublic() << std::endl
<< “cPub.get_Pub_mPrivate(): ” << “does not exist!” << std::endl
<< “cPub.get_mPrivate(): ” << ” inaccessible, a private Base method!” << std::endl
<< “cPub.get_Pub_mProtected(): ” << cPub.get_Pub_mProtected() << “n”;
std::cout << “n … creating cPri”;
Pri cPri;
// Fill the blank below
// 1. to modify the value of the private data memeber of the base class to (4, 5, 6),
// no need to explore the modification by the setter() method.
// 2. to retrieve and display the value of base class data members via either
// cPro class methods, if possible.
// 3. If the private data member of the base class can not be accessed, explain.
std::cout << “n … creating cPro”;
Pro cPro;
// Fill the blank below, same requirement as above.
// However, we can still can access Base members as normal through Base:
Base cBase;
cBase.mPublic = 4; // okay, mPublic is public
//cBase.mPrivate = 5; // not okay, mPrivate is private
//cBase.mProtected = 6; // not okay, mProtected is protected
std::cout << ” … access cBase by applicationn”
<< “cBase.mPrublic: ” << cBase.mPublic << std::endl
<< “cBase.mPrivate: ” << “inaccessible, a private member!” << std::endl
<< “cBase.mProtected: ” << ” inaccessible, a protected member!” << std::endl;
}
